Mayflies is one of the most important insects that form a part of your swiftlet's diet. They are commontly found breeding in rivers,lakes, pond and astuaries. They are beautiful, soft bodies, fragile beauty and short adult lifespan, usually a few days to mate and die.
Mayflies live as nymphs for 3 months to 2 years, depending on the species. When they're mature, the entire generation emerges from the stream as adults, often within the span of a couple weeks.
They emerge as "duns," an immature winged adult stage, and molt within a day or two into "spinners," the mature adults.
The duns most often emerge during an hour or two each day for a couple weeks sometime in the spring or summer, though there's great variation between species. These events are barely noticeable in some species and reach nightmarish proportions in others.
There are three ways mayfly nymphs emerge into duns. Most often, the nymph swims to the water's surface and splits open its exoskeleton above the thorax (Thorax: The thorax is the middle part of an insect's body, in between the abdomen and the head, and to which the legs and wings are attached.).
The dun wriggles out onto the surface, and many species float along on the surface for a while as their wings dry. These species make prime targets for hungry fish, and they are the dry fly fisherman's favorites. But many important species don't follow this pattern.
In a some species, the winged dun emerges from its nymphal case several feet underwater and swims to the surface, wings and all. Old-style winged wet flies match these hatches, but newer sparkle yarn patterns work better.
Other species emerge by crawling out onto streamside rocks or logs as nymphs. The adults emerge there on land.
Once mayflies have molted into spinners, they usually gather in swarms over the river to mate. When they're done they usually fall dead, or spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.), on the water.
Mayfly females face the extra duty of laying their eggs after mating. Many species release their eggs as they fall spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.) on the water.
Some land on the water, release a few, and take off again. Others fly low over the water and tip the tips of their abdomens below the surface for just a moment to release eggs. Other species drop their eggs from high in the air. In one very common genus, Baetis, the females land near shore and crawl underwater to lay their eggs in neat little rows on rocks and logs.
Like most things in nature, mayfly spinners aren't as predictable as we'd like. Sometimes clouds of thousands of spinners will gather over a riffle in the evening and fly back into the woods as quickly as they came, never falling spent.
Spinner falls can happen at any time of day, depending on species, but dusk is by far the most common time. These events are usually much more concentrated than the dun emergence of the same species, which means that many species which are unimportant as duns due to sporadic emergence become very important as spinners.
Some spinner falls take place over every type of water, but most species choose riffles.
No comments:
Post a Comment